Electrode chemical control system and method

ABSTRACT

A method and system for controlling an electroless deposition process are provided. The system generally includes an electroless plating cell having a work piece to be plated positioned therein, the work piece also being positioned in communication with an electroless plating solution contained by the plating cell, and a voltage measurement device in communication with the work piece and the electroless plating solution, the voltage measurement device being configured to measure the electrical potential difference between the work piece and the plating solution. The system further includes a control voltage device in communication with the work piece and being configured to apply a determined control voltage to the work piece, and a system controller in communication with the voltage measurement device and the control voltage device, the system controller being configured to receive an input from the voltage measurement device and to generate a control voltage output corresponding to the determined control voltage, the output being sent to the control voltage device to cause the control voltage device to apply the determined control voltage to the work piece.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the priority under 35 USC §119 of U.S. Provisional Patent Application No. 60/864,952 filed Nov. 8, 2006, the disclosure of which is hereby incorporated herein by reference.

BACKGROUND OF THE INVENTION

Electroless plating, also known as chemical or auto-catalytic plating, is a non-galvanic type plating method that generally involves simultaneous chemical reactions taking place in an aqueous plating solution to deposit or “plate” a selected material, often a metal or conductive material, onto a plating surface. Electroless plating, unlike electrolytic plating, does not require any external source of electrical current to sustain the plating reaction. Rather, electroless plating involves an autocatalyzed chemical deposition process that continues without the application of any external applied current, assuming the conditions are met for the chemical reaction to take place. A typical electroless plating chemical reaction generally involves exposing a substrate to an electroless plating solution by immersing the substrate in the solution or by spraying the solution over the substrate. The electroless solution chemically reacts with the surface of the substrate to form a plated layer on the substrate surface. The surface to be plated must generally be capable of electron transfer for nucleation and deposition of the plated material to occur over that surface, and therefore, non-metal surfaces and oxidized surfaces are examples of surfaces which seldom participate in electron transfer, and thus, generally is not plated via an electroless plating process. These surfaces will generally need to be coated with a conductive seed or barrier layer that is capable of electron transfer before they may be plated with an electroless plating process.

In the semiconductor industry, electroless plating is regularly used to form capping layers, to fill trenches and vias with conductive material, and to selectively deposit conductive materials onto various surfaces. Currently, copper and copper alloys have become the metals of choice in the semiconductor industry, as copper provides low electrical resistivity, a high current carrying capacity, and favorable thermal conductivity and electromigration resistance characteristics. These characteristics are important for supporting the higher current densities experienced at high levels of integration and increased device speed. Additionally, copper is a favored metal as it has shown to be effectively deposited by both electrolytic and electroless deposition techniques, both of which are well understood by the semiconductor industry.

However, one challenge presented by electroless plating processes is that the plating process presents some difficulty to accurately control. More particularly, the initiation the chemical reactions needed to support electroless plating processes are heavily dependent upon temperature. The initiation time, which is generally defined as the time it takes the electroless deposition process to begin (for the catalytic fluid layer) or deposition fluid to begin interacting with the plating surface), is heavily dependent upon temperature. Once the electroless plating reaction begins, the time to deposit a defined amount of material is generally predictable and will generally fall into a relatively repeatable range of deposition rates under similar processing conditions. However, since it is very difficult to know when the process has initiated and the initiation time varies from substrate to substrate or from one area of a substrate to another it is hard to know when the desired thickness of material has been deposited across the surface of the substrate. Further, temperature variations during electroless plating processes significantly impact on the rate and quality of the material being plated. Therefore, electroless plating processes present significant challenges to controlling the plating process itself.

As such, there is a need in the art for a method and system for accurately controlling electroless plating processes.

SUMMARY OF THE DISCLOSURE

Embodiments of the disclosure provide a system and method for controlling an electroless plating process. The system may generally include an electroless plating cell having a work piece to be plated positioned therein, the work piece also being positioned in communication with an electroless plating solution contained by the plating cell. The system may also include a voltage measurement device in communication with the work piece and the electroless plating solution, the voltage measurement device being configured to measure the electrical potential difference between the work piece and the plating solution, and a control voltage device in communication with the work piece and being configured to apply a determined control voltage to the work piece. The system may further include a system controller in communication with the voltage measurement device and the control voltage device, the system controller being configured to receive an input from the voltage measurement device and to generate a control voltage output corresponding to the determined control voltage, the output being sent to the control voltage device to cause the control voltage device to apply the determined control voltage to the work piece.

In another exemplary embodiment, a method for controlling an electroless deposition process is provided. The method may include measuring an electrical potential at a plating surface during an electroless deposition process, comparing the measured electrical potential to desired electrical potential for the electrical deposition process, and applying a control voltage to the plating surface to adjust the electrical potential at the plating surface to be closer to the desired electrical potential.

In another exemplary embodiment of the invention, a system for controlling an electroless deposition process is provided. The system may include a measuring means for measuring an electrical potential at a plating surface during an electroless deposition process, a control means for comparing the measured electrical potential to desired electrical potential for the electrical deposition process, and a voltage generating means for generating a control voltage that is communicated to the plating surface to adjust the electrical potential at the plating surface to be closer to the desired electrical potential.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a high level block diagram of an exemplary electroless deposition control system;

FIG. 2 illustrates a more detailed diagram of an exemplary electroless deposition control system; and

FIG. 3 illustrates a flowchart of an exemplary electroless deposition control method.

DETAILED DESCRIPTION

Embodiments of the invention generally provide a system or method for controlling an electroless deposition process. The exemplary system and method are generally configured to monitor an electrical potential generated at the plating surface, and to apply a control voltage to the plating surface to optimize the plating process, to slow the plating process, or to stop the plating process, as desired. Throughout the specification references made to plating or deposition are intended to refer to an electroless plating process whereby a chemical reaction near the surface of a work piece causes a layer of material to form on the surface of the work piece. This layer will generally grow in thickness as the chemical reaction continues. Further, the phrase “plating cell” is used throughout the specification, however, the phrase is not intended to be construed to mean any particular type, size, or configuration of plating cell. Rather, the phrase is intended to apply to any type, size, or configuration of device or apparatus that is configured to support a plating process. As such, this definition includes cells ranging from nano-technology cells, to beaker-type cells, all the way up to flat panel display sized plating cells that may span several meters.

Prior to addressing the specific embodiments of the invention, Applicants note that it is to be understood that the following disclosure provides many different embodiments, or examples, for implementing different features of various embodiments of the invention. The exemplary embodiments described herein discuss components and arrangements only as examples, and are of course, not intended to be limiting. In addition, the present disclosure may repeat reference numerals and/or letters in the various exemplary embodiments. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. Moreover, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed interposing the first and second features, such that the first and second features may not be in direct contact. Similarly, method steps or program step execution sequences that are not expressly recited as being in a specific order may be conducted in various sequences and are not intended to be limited by the order in which they are described in the exemplary embodiments of the invention discussed herein.

Further still, various exemplary embodiments of the invention are described herein, and the invention is not intended to be limited to any particular exemplary embodiment. Rather, the inventors contemplate that the invention, as evidenced by the claims, may include any combination of the exemplary embodiments described herein and the equivalents thereof.

Further still, in general, software routines implementing various elements, parts, or embodiments of the present disclosure, including the control system generally described herein, may be included as part of a computer operating system or as part of a specific application, component, program, module, object, or sequence of instructions, such as an executable script. Software routines typically include a plurality of instructions capable of being performed using a computer system or other type or processor configured to execute instructions read from a computer readable medium. Also, programs typically include or interface with variables, data structures, other computer programs that reside in a memory or on storage devices as part of their operation. In addition, various programs described herein may be identified based upon the application for which they are implemented. Those skilled in the art will readily recognize, however, that any particular nomenclature or specific application that follows facilitates a description of embodiments of the present disclosure and does not limit the embodiments for use solely with a specific application or nomenclature. Furthermore, the measuring, comparing, and generating functionalities of the control system or programs supporting the control system herein may use a combination of discrete modules or components interacting with one another. Those skilled in the art will recognize, however, that different embodiments may combine or merge such components or modules in a variety of ways not expressly recited in the exemplary embodiments described herein.

FIG. 1 illustrates a high level block diagram of an exemplary electroless deposition control system of the invention. The exemplary electroless control system 100 includes an electroless plating cell 102, an electrical potential measurement device 104, and a corrective electrical potential generation device 106. The electroless plating cell 102 may be any type or configuration of plating cell used to support electrochemical, chemical, or auto-catalytic plating processes. Two types of plating cells used in the semiconductor processing technology field for electroless plating include overflow weir type plating cells and spray on-type plating cells, both of which are applicable to the exemplary embodiments described herein. The electrical potential measurement device 104 is generally a device configured to take a voltage measurement of an electrical potential at a plating surface of an object being plated during an electroless plating process. Electroless plating processes are known to generate an electrical potential at the surface of the work piece as a result of the chemical reaction causing an electron transfer (and nucleation) to occur at the plating surface. The electrical potential generated by the chemical reaction in an electroless plating process is known to be directly related to the plating rate of the electroless chemical reaction. Therefore, the measurement of the electrical potential in the present exemplary embodiment may be used to mathematically determine the plating rate of the electroless plating process at the time of the electrical potential measurement.

Additionally, in an exemplary embodiment of the invention, the electrical potential measurement device 104 may also include a temperature sensor. The temperature sensor may be in communication with the plating solution or other processing environment in the plating cell 102. The temperature sensor may be configured to determine the temperature of the processing fluid (the electroless plating solution) or the processing environment in the plating cell 102.

The electrical potential measurement may be conducted at predetermined intervals, randomly, or in response to a control system 108 input instruction. The control system 108 may be any type of controller configured to receive and process inputs, and in response thereto, generate outputs in accordance with a predetermined control program, sequence, or logic. In one exemplary embodiment of the invention, the control system 108 may be a microprocessor configured to receive input signals and generate output signals in accordance with a control program running on the microprocessor. At least one output of the control system 108 may be in communication with the corrective electrical potential generation device 106. The corrective electrical potential generation device 106 may be a system, device, or apparatus configured to generate a specific electrical potential in response to an input control signal. As such, the control system 108 may generate an output signal representative of a particular voltage that is communicated to the corrective electrical potential generation device 106. The corrective electrical potential generation device 106 may receive an input from the control device 108, and in response thereto, generate an electrical potential at an output of the corrective electrical potential generation device 106 that corresponds to the particular voltage requested by the control system 108 in the output signal. The output of the corrective electrical potential generation device 106, i.e., the specific electrical potential voltage called for by the control system 108, may be communicated to the electroless plating cell, and more particularly, to the plating surface of the work piece. The specific electrical potential voltage, therefore, may be used to control the electroless plating process.

In another exemplary embodiment of the invention, the corrective electrical potential generation device 106, the electrical potential measurement device 104, and the control system 108 may be combined into a single unit configured to monitor the electrical potential at the plating surface of the work piece and apply a control voltage to the working surface to control the electroless plating process. The control voltage or electrical potential applied to the plating surface operates to adjust the rate at which the electroless chemical reaction deposits material onto the plating surface. More particularly, the applied voltage or potential can be used to decrease or stop the electroless deposition reaction to control the thickness or quality of the material being deposited.

FIG. 2 illustrates a more detailed diagram of an exemplary electroless plating cell having an exemplary deposition control system. The exemplary electroless plating cell and control system 200 generally includes a plating cell 202 configured to contain an electroless plating solution. The solution may fill a portion of the plating cell 202, i.e., up to a fill line 204, which may be positioned such that a substrate or work piece 208 may be positioned in the plating cell 202 in a manner that exposes or even submerges the working surface of the substrate into the electroless solution contained in the plating cell 202. The exemplary plating cell 202 may include an enclosure 214 that seals the interior or processing portion of the plating cell 202 from ambient conditions and contaminants. The enclosure 214 may be selectively removable or may contain a selectively operable access door or window that may be used to transfer substrates or work pieces into and out of the processing environment.

The interior of the exemplary plating cell 202 contains a substrate support member 206 that is configured to support a substrate or other work piece during processing. In one exemplary embodiment, the work piece may be a round 150 mm, 200 mm or 300 mm silicon based semiconductor substrate, and therefore, the substrate support member 206 may be a substantially round support member configured to receive and support semiconductor substrates for processing. The present invention is not intended to be limited to any particular substrate or work piece. The inventors contemplate that the electroless control process may be used on any type of work piece, including square substrates, glass substrates, printed circuit boards, and any other material that can be plated.

The substrate support member 206 generally includes an electrical contact member 212 that is configured to electrically contact the work piece at a perimeter thereof. The electrical contact member 212 may by manufactured from any conductive material, however, manufacturing the electrode from a material that is inert to electrochemical reactions may facilitate more accurate voltage measurements, as non-inert materials will facilitate an electrochemical reaction to take place on the electrode itself, which may skew the accuracy of the potential measurements for the entire substrate or work piece. The electrical contact member 212 may be an electrical contact ring or other electrical contact device used in the semiconductor processing industry that is configured to electrically contact a substrate or work piece surface without interfering with the deposition process. Generally, these types of contact rings and devices are configured to electrically contact the surface of substrates and work pieces very near the perimeter, e.g., within 1.5-5 mm of the edge, of the substrates or work pieces in an area generally referred to as the exclusion zone. The exclusion zone is generally known to be an area of the substrate or work piece that will not be used for production, and as such, the zone may be used for securing and electrical contact without impacting the performance or integrity of the devices produced from the substrate.

The interior of the plating cell 202 may also contain an electrode 210 that is in communication with the control system 108, the corrective electrical potential generation device 106, and/or the electrical potential measurement device 104. The electrode 210 may generally be an inert electrode that will not react with the electroless plating solution. As such, the electrode may be a titanium electrode having a platinum layer plated thereon. The electrode 210 is configured as a reference/auxiliary electrode for measuring the electrical potential at the surface of the substrate or work piece. Thus, the electrical potential difference between the electroless plating solution in the plating cell and the plating surface where the electroless chemical reaction is taking place can be measured by determining the electrical potential difference between the electrode 212 and electrode 210.

The electrode 210 or the electrode 212 may also include a temperature sensor that is in communication with the control system 108, the electrical potential measurement device 104, or the corrective electrical potential generation device 106. Alternatively, a separate temperature sensor may be positioned in the plating cell 202. The temperature sensor is generally configured to measure the temperature of the plating solution in the plating cell 202. The plating cell 202 may further include a heating unit 216 configured to selectively increase the temperature of the plating solution. The heating unit 216 may be in communication with a control system, such as control system 108, that is configured to maintain the plating solution in the plating cell at an optimal temperature for electroless processing.

In operation, embodiments of the invention provide an electroless plating cell having a control system in communication therewith, wherein the control system is configured to cooperatively monitor an electrical potential voltage at a plating surface and a temperature of a plating solution in the plating cell to control an electroless plating process. FIG. 3 illustrates a flowchart of an exemplary electroless deposition control method of an exemplary embodiment of the invention. The exemplary method begins at 300 and continues to steps 301 and 302. At step 301, the voltage at the plating surface of the substrate or work piece is measured and communicated to a control system. Similarly, at step 302, the temperature of the plating solution in the plating cell is measured and communicated back to the control system. Both the electrical potential and the temperature measurements are generally real time measurements that are taken during processing. Once the measurements of the electrical potential and the temperature are taken, the measurements are communicated to the control system, and at step 303, the control system determines if a control voltage should be applied to the substrate being plated to control the plating rate. If the control system determines that a control voltage is necessary, then at step 304 the control voltage is generated and applied to the substrate being plated.

In the situation where the control system determines that no control voltage is necessary (at step 303), then the method returns to the monitoring phase at steps 301 and 302. The control system of the exemplary embodiment may be configured to continually loop through steps 301 and/or 302 and step 303 to continually monitor the plating process to determine if a control voltage should be applied to the plating surface.

In another exemplary embodiment of the invention, the control system may use the temperature monitoring to determine if the processing conditions are able to support adequate plating. More particularly, electroless plating processes are known to be heavily dependent upon temperature, and that both the plating rates and the quality of the deposited layers often degrade when the temperature of the plating solution falls below an optimal temperature. Therefore, in the present exemplary embodiment, the temperature of the electroless plating solution may be determined at step 302, and then at step 303, the temperature can be compared to an optimal processing temperature range for the particular electroless deposition process being conducted. If the measured temperature is not within the range of optimal processing temperatures, then the control system may determine that a voltage should be applied to the plating surface to stop the plating process until such time that the measured temperature of the plating solution is within the optimal temperature range for processing.

If the control system determines that a voltage should be applied to stop the plating process at step 303, then at step 304 a stop voltage is applied to the substrate. The stop voltage is generally calculated to be of equal magnitude to the voltage measured at the surface of the substrate during plating, however, the stop plating voltage is of the opposite polarity of the measured voltage. Thus, the application of an equal magnitude and opposite polarity voltage to the plating surface results in a net zero voltage at the plating surface, which operates to stop the electroless plating process. For example, if the measured voltage at the surface of a work piece during a plating process is −0.8 volts, then the stop voltage to be applied to the substrate would be +0.8 volts.

In another exemplary embodiment of the invention, the control voltage may be applied to decrease the plating rate of an electroless deposition process. In this embodiment, once the voltage at the plating surface is measured, then a voltage of opposite polarity and of a lesser magnitude may be applied to slow the plating rate of the electroless deposition process. For example, if the voltage measured at a plating surface is −0.8 volts, and the desired voltage at the plating surface for optimal deposition is −0.6 volts, then the control system of the exemplary embodiment can apply a +0.2 volts to the plating surface to slow the electroless plating reaction to the optimal rate.

In yet another exemplary embodiment of the invention, the temperature of the plating solution may be adjusted to increase the plating rate of the electroless deposition process. In this embodiment, if the measured voltage at the plating surface is less than a desired optimal voltage for the particular electroless deposition process being used, then the control system can adjust the parameters of the plating process to increase the plating rate of the electroless deposition process. One parameter that can be adjusted is the temperature of the plating solution. For example, if the voltage measured at the plating surface is −0.6 volts and optimal plating occurs at −0.8 volts, then the control system may activate a plating solution heater, such as heater 216 in the exemplary embodiment illustrated in FIG. 2, to increase the temperature of the plating solution. The increase in the temperature of the plating solution will generally operate to accelerate the electroless plating process, and therefore, increase the magnitude of the measured voltage at the plating surface. Therefore, ideally the temperature of the plating solution would be heated until the measured voltage at the plating surface was at the optimal voltage level, and then the temperature of the solution would be maintained at that particular temperature.

In yet another exemplary embodiment of the invention, the measured voltage at the plating surface of the plating solution may be adjusted to increase the plating rate of the electroless deposition process. In this embodiment, if the measured voltage at the plating surface is less than a desired optimal voltage for the particular electroless deposition process being used, then the control system can adjust the parameters of the plating process to increase the plating rate of the electroless deposition process. One parameter that can be adjusted is the voltage at the plating surface. More particularly, the control system may apply a voltage to the plating surface to increase the plating rate of the reaction. For example, if the measured voltage at the plating surface is −0.6 volts and optimal plating occurs at −0.8 volts, then the control system can apply a voltage of −0.2 volts to the plating surface to facilitate the plating process. However, application of a cathodic voltage to the plating surface may initiate a hybrid plating process, where an electroless reaction is taking place and the cathodic voltage causes a simultaneous electrolytic plating process to begin. This combined plating process may continue for a short period of time until, for example, the temperature of the electroless plating solution can be increased so that the electroless deposition process alone generates an acceptable plating rate so that the electrochemical reaction can be terminated (by removing the cathodic voltage). Combined electrochemical and electroless plating reactions is generally undesirable for long periods of time, as the solutions generally contain different constituents or additives that are not favorable for the other deposition process. For example, the organic additives used in an electroless solution for leveling, suppressing, and accelerating plating at certain areas are consumed at a very high rate when an electroless solution is subjected to an electrochemical plating process.

In another exemplary embodiment of the invention, the sensing (voltage at the plating surface) and application of the control voltage are accomplished during independent windows. The voltage measurement process and the voltage application process are generally conducted at separate times to prevent interference during the measurement and control procedures. Therefore, embodiments of the invention may implement specific time windows where control voltages are applied to the plating surface, but where no measurements of the voltage at the plating surface are taken. Similarly, embodiments of the invention may implement specific time windows where voltage measurements at the plating surface are taken, but where no control voltages are applied. These discrete windows for measuring and applying voltages operate to isolate the respective events from each other and prevent distortion of the measurement process, which results in more accurate electroless plating control.

In another exemplary embodiment of the invention, the exemplary control system may be used to prevent an electroless deposition process from initiating or starting until the processing conditions are within an optimal range. For example, an electroless deposition process is generally conducted with the electroless solution at a specific temperature. If the solution is not at the desired operating temperature, then the control system of the invention may be used to apply a control voltage to the substrate or plating surface that is calculated to prevent the electroless deposition process from starting. This control voltage may be continually applied to the substrate until the temperature of the plating solution can be brought into the optimal temperature range.

The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art will appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions and alterations herein without departing from the spirit and scope of the present disclosure. 

1. A system for controlling an electroless deposition process, comprising: an electroless plating cell having a work piece to be plated positioned therein, the work piece also being positioned in communication with an electroless plating solution contained by the plating cell; a voltage measurement device in communication with the work piece and the electroless plating solution, the voltage measurement device being configured to measure the electrical potential difference between the work piece and the plating solution; a control voltage device in communication with the work piece and being configured to apply a determined control voltage to the work piece; and a system controller in communication with the voltage measurement device and the control voltage device, the system controller being configured to receive an input from the voltage measurement device and to generate a control voltage output corresponding to the determined control voltage, the output being sent to the control voltage device to cause the control voltage device to apply the determined control voltage to the work piece.
 2. The system of claim 1, wherein the determined control voltage is calculated by the system controller to decrease a plating rate of the electroless deposition process.
 3. The system of claim 1, further comprising a temperature sensor in communication with the system controller; the temperature sensor being positioned to measure a temperature of the electroless plating solution in the plating cell.
 4. The system of claim 3, wherein the system controller is configured to generate a control voltage output calculated to stop the electroless deposition process when the temperature sensor senses that temperature of the electroless plating solution is outside of an optimal plating temperature range.
 5. The system of claim 1, wherein the voltage measurement device comprises a first inert electrode positioned in the plating cell in communication with the plating solution, and a second electrode positioned in communication with a plating surface of the work piece.
 6. The system of claim 5, wherein the first and second electrodes are in communication with a voltage measuring device configured to determine the electrical potential difference between the first and second electrodes.
 7. The system of claim 4, further comprising a heating unit positioned and configured to heat the electroless plating solution, the heating unit being in communication with the system controller.
 8. The system of claim 7, wherein the system controller is further configured to activate the heating unit in combination with generating the control voltage output calculated to stop the electroless deposition, the heating unit being activated until the temperature of the electroless plating solution is measured to be within the optimal plating temperature range.
 9. A method for controlling an electroless deposition process, comprising: measuring an electrical potential at a plating surface during an electroless deposition process; comparing the measured electrical potential to desired electrical potential for the electroless deposition process; and applying a control voltage to the plating surface to adjust the electrical potential at the plating surface to be closer to the desired electrical potential.
 10. The method of claim 9, wherein measuring the electrical potential at the plating surface comprises positioning a first electrical potential measuring electrode in communication with the plating surface and positioning a second electrical potential measuring electrode in communication with an electroless plating solution.
 11. The method of claim 10, wherein the second electrical potential measuring electrode is manufactured from an inert material that does not react with the electroless plating solution.
 12. The method of claim 10, wherein the first and second electrodes are in communication with a voltage measuring device.
 13. The method of claim 10, further comprising measuring a temperature of the electroless plating solution and stopping the electroless deposition process if the temperature of the electroless plating solution is not within a desired temperature range for the particular electroless deposition process.
 14. The method of claim 13, wherein stopping the electroless deposition process comprises applying a voltage to the plating surface that is equal in magnitude and opposite in polarity to the measured electrical potential at the plating surface.
 15. The method of claim 14, further comprising heating the electroless plating solution to a temperature within the desired temperature range while the electroless deposition is stopped.
 16. The method of claim 15, further comprising restarting the electroless deposition process by removing the voltage applied to the plating surface that is equal and opposite in magnitude to the measured electrical potential at the plating surface.
 17. The method of claim 9, wherein the measuring and applying are conducted independently at separate times.
 18. The method of claim 9, wherein the control voltage is calculated to decrease a deposition rate of the electroless deposition process.
 19. The method of claim 9, wherein the control voltage is calculated to stop an electroless deposition supporting chemical reaction taking place at the plating surface.
 20. A system for controlling an electroless deposition process, comprising: measuring means for measuring an electrical potential at a plating surface during an electroless deposition process; control means for comparing the measured electrical potential to desired electrical potential for the electrical deposition process; and voltage generating means for generating a control voltage that is communicated to the plating surface to adjust the electrical potential at the plating surface to be closer to the desired electrical potential.
 21. The system of claim 20, further comprising a temperature sensing means for measuring a temperature of an electroless plating solution.
 22. The system of claim 21, wherein the control means is configured to cooperatively operate with the voltage generating means to stop the electroless deposition process if the temperature of the electroless plating solution is outside of a desired temperature range.
 23. The system of claim 22, wherein the voltage generating means is configured to apply a voltage that is equal in magnitude and opposite in polarity to the measured electrical potential at a plating surface to stop the electroless deposition process.
 24. The system of claim 20, wherein the control voltage is calculated to decrease a deposition rate of the electroless deposition process. 